Structural adhesives are a good alternative to other mechanical techniques for binding two materials together, such as metals or plastics. This is because there is better force distribution by bonding than when alternative techniques such as riveting or welding are used. In addition, the use of bonding often allows more rapid working and also has the advantage of providing better insulation from external elements (dust, moisture) than mechanical technologies.
Structural adhesives are thus used in many industrial fields, even though they do have certain disadvantages. In fact, the bond created during the curing (setting) of the adhesive is often rigid when good mechanical strength is necessary. Thus, if the elasticity of the adhesive is insufficient, fracture may be observed when the two parts bonded together are made to undergo forces moving them apart. Adhesives having good elasticity do exist, but they are often of low mechanical strength.
It is therefore necessary to identify structural adhesives having both good mechanical strength (especially shear strength) and satisfactory elasticity. Moreover, it is important for these properties to be observed on various types of material, and especially on metal and on composites. Finally, it is important that these adhesives have a high viscosity so as to be able to be applied over great lengths on vertical or overhanging surfaces without slipping or flowing off before the application of the second surface to be adhered thereto. This phenomenon is particularly annoying when a long working time is necessary.
This slip phenomenon reduces for example the use of acrylic-based adhesives for applications requiring the adhesion of long objects to panels. The fact of trying to use these adhesives can increase the construction time or complicate the manufacturing process.
The development of adhesives for such a use would make it possible to simplify the methods requiring the adhesion of two large areas, to vary the construction materials and to speed up these methods.